Shear members are used to hold components together until a predetermined shear force is applied at which point the shear member fails by design. Shear members are frequently elongated cylindrical solid shapes or they can be annular hollow shapes such as a roll pin. Another variation for concentric members to hold them fixed against relative axial movement until a predetermined time is an l-shaped ring where one component is supported by the fixed member and the other portion of the l-shape is supported by the movable member. The shear location is generally at the vertex of the l-shape.
The problem with these designs apart from uncertainty regarding the amount of force that needs to be applied to cause them to fail is that post shear there are segments that can cause problems if for example there is not a clean break or if one of the segments after the shear comes out of the member to which it was initially mounted. Typically the shear members are inserted in a clearance or interference fit in aligned bores. In these situations, the segment can score the opposing member when the relative movement occurs. Equally as bad is that the segment can come loose and wedge the member trying to move with respect to its opposite member and a parts jam could result which disables a tool forcing at best an unnecessary trip out of the hole or even worse a potentially hazardous situation.
Various techniques have been used to mount shear pins as illustrated in U.S. Pat. Nos. 4,102,153; 6,287,079; 5,259,015 and 6,546,689.
The present invention seeks to address this issue in a subterranean context by employing simple structures that accomplish the intended purpose while at the same time taking up minimal space and facilitating rapid assembly. Means are provided in place of the clearance or interference fit used in the past of retaining at least one of the components internally in the respective bores in which the frangible member is disposed before the shear event. Those skilled in the art will better appreciate additional aspects of the invention from a review of the description of the preferred embodiments and the associated drawings while recognizing that the full scope of the invention is to be determined from the appended claims.